Hi,
I also have a shunt from my 1988 surgery but it's probably different than yours. I developed a condition after surgery called Normal Pressure Hydrocephalus where my MRI scan looked normal (no CSF buildup on the scan) but I had terrible headaches, vomiting and fluid build-up under the incision that would not go away. This shunt allowed me to start healing. During this ordeal I was explained that CSF build-up is worse after lying down after a few hours such as first thing in the morning after a full night of sleep. That is why headaches in the morning is an ominous sign as it can signify a brain tumor. Double vision in the morning all of a sudden CAN be a sign of hydrocephalus as well but only a specialist can decide whether it is indeed. My shunt was put in by Dr. Wisoff of NYU. He told me that all functioning shunts need periodic revisions and none function longer than 10 years. The fact that mine is 20 years old means that it no longer works and I don't need it. They can test the shunt in the office if I want to.
Here is my suggestion:
1) Sleep on elevation (many pillows, wedge pillows) or sitting up (Lazy Boy chair or any very comfortable chair). This allows for an optimal flow of CSF and prevents its build-up. Note if there are any changes in the frequency of double vision in the morning.
2) Seek out a specialist in shunts in your area. The shunts are most common in pediatric and elderly populations and are uncommon among adults unless they have been "blessed" with a big brain tumor. In my experience these specialists are listed under "pediatric neurosurgeons", so you might have to make a lot of phone calls before you find one. There are actually people whose bread and butter is shunts, not surgery. These specialists are well hidden but they do exist.
3) Seek out the advice of neuro-opthalmologist as Steve has suggested. All these options are not mutually exclusive. The more specilists you see, the more you will find out about the cause of your double vision.
4) Seek consultation of your original neurosurgeon even if it is only by phone or e-mail.
I would love to know where you had your original surgery, who did your shunt and how big was your tumor. I am assuming it was big, otherwise you would not need a shunt to begin with. Best of luck to you and let us know how you are doing.
Eve